Dimers oroidin-like

The excellent reviews of Berlinck [1-5] have surveyed a great number of guanidine-type natural products. In addition, some guanidine-derived marine alkaloids have been reviewed by Kobayashi and Ishibashi [6,7]. Also, a recent book gave accounts of marine alkaloids including the phakellins, palau amines and oroidin-like dimers derived from bromopyrroles and polyketide-derived polycyclic guanidine alkaloids [8]. 

Figure 9. Oroidin-like dimers sceptrin (63) and its analogues 64-69.

Figure 10. Oroidin-like dimers konbu acidin A (70), axinellamines A-D (71-74), and massadine (75).

Home was able to provide support for the biosynthetic hypothesis that mauritiamine (197) results from dimerization of an oroidin-like species. Upon examination of the natural product stmcture, it appears to be the union of oroidin (25) and dispacamide (196) (Scheme 13.34). Home was able to dimerize vinyl aminoimidazole 26 under oxidative conditions to provide the core of mauritiamine (199) [130]. After installation of the dibromopyrroles via acylation, the natural product was realized in six steps from ornithine methyl ester (198), without the need for PGs. 

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